1. Field of the Invention
The present invention relates to a foothold of a manhole, a quay, etc., comprising a tread and side portions continued from and positioned at both sides of the tread.
2. Prior Art
A conventional foothold of a manhole, a quay, etc., of this type is disclosed, for example, in JP-Y 4-4040 in which a tread and side portions continued and positioned at both sides of the tread and they are positioned to be flush with each other when viewed from the side thereof, and the upper surface of the tread is linear and flat.
However the conventional foothold of a manhole has the following problem. That is, when operators move up and down in the manhole by use of a plurality of footholds arranged in the manhole, a quay, etc., they move up and down in an unstable condition where they are liable to miss their footing from the tread and also they are fatigued with their feet or knees since the upper surface of each tread is linear and flat.